Reply To: GREP Styles – Is this possible?

You could just use nested styles, which would be easier. When making the nested style, click on the word “Words” (which gives you a popup menu of options, such as Sentences, Characters, etc.). Instead of choosing from the menu, type : – (colon, hyphen) or use em dashes or whatever. The character style will span “up to” or “through” (depending on what you choose) whichever character it comes to first.

That is, if you type .,! then it'll extend to the first period, comma, or exclamation point.